Number of minute stones

William Benjamin Carpenter,  Animal Physiology, Londres, H.G. Bohn, 1859, p. 532-533.

The aquatic Larvae of the Caddice-flies (fig. 273, c), which are commolly known as Caddice- worms, house themselves in straws, pieces of hollow stick, rushes, &c.; and those of some species glue together a number of minute stones, pieces of stick, small shells, &c., so as to make a tube (A), in which the animal creeps along the bottom and sides of the brook it inhabits, and sometimes rows itself on the surface of the water.